Minami Ritsu (南律)
A menacing figure. He is Soubi's former teacher, and the two have a very twisted relationship. It is not stated explicitly, but in a flashback chapter Nagisa blames Ritsu for taking Soubi's ears. She accuses him of doing it because Soubi resembles his late mother, whose death was the reason Ritsu took charge of Soubi to begin with. Even so, Ritsu claims he hated her. It is also shown that when Soubi was 17, he expected Ritsu to take him as his fighter. Still, as Soubi himself said, "It isn't love or hate. There isn't anyone else."
Commonly mistaken for a member of Septimal Moon, in volume 5 Ritsu says he nor Nagisa are members of the group.